|
|
From: "Al Gietzen" <ALVentures@cox.net>
Date: 2004/10/19 Tue AM 10:29:24 EDT
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: EWP
I understand the EWP has higher efficiency than the stock pump - does
someone know how much? (I may have missed it because I haven't followed this
issue very closely). But I'm sure it is less than 40% better. And you can
save some pumping power in some flight regimes where the belt driven pump is
pumping more flow than needed. But, overall, saving power is not a likely
reason for going to an EWP.
Configuration - yes. Redundancy - yes. Power saving - not.
Al
Al,
I wonder if you misunderstood the nature of the question and of my reply. I keep saying that I shouldn't reply to messages at 0-dark-30 when I can't sleep, but I keep doing it. Still, the question wasn't whether to convert or not but whether or not to use the controller.
The belt-driven water pump has to be able to provide cooling flow under worse-case conditions: low-speed city traffic. Therefore, it is way over capacity at 6500 RPM.
This can be mitigated somewhat by changing pulley sizes, but at the risk of the cooling at idle and taxiing. The electric pump allows demand-based flow, using only as much energy as necessary to provide adequate cooling at that moment.
Not using the controller, leaves three basic options: (A) wire direct, pumping full flow all the time and using a thermostat to maintain minimum heat.
(B) wire direct, with no thermostat, and run cold during decents and other low-load conditions.
(C) Put in a manual speed control.
Rusty's concern - inadequate "minimum" flow speed - can be dealt with fairly easily.
It would seem to me that the only time the pump needs to be at maximum output is during climb-out. The rest of the time, the system needs significantly less flow and therefore considerably less input. How much? That *does* yet need to be evaluated, but the experience of the racers seems to indicate that it is not trivial.
Dale R.
COZY MkIV #1254
|
|